Waveform generators are widely used in switching power supply devices, function generators, filter tuning circuitry and motor driving devices.
A conventional sinusoidal waveform generator generally comprises two stages. The first stage is a triangle waveform generator and the second stage is a converter which converts the triangular waveform to a sinusoidal waveform. The triangular waveform generator generally comprises a current source, a polarity switch and a means of capacitance, such as one or a plurality of capacitors. The triangular-to-sinusoidal converter generally comprises several diodes and resistors. The triangular-to-sinusoidal converter takes advantage of a diode's nonlinear function to rectify and shape the waveform.
Disadvantageously, the nonlinear functions of the diodes in the conventional triangular-to-sinusoidal converter typically require as many current paths as there are diodes. As a result, the triangular-to-sinusoidal converter has high power consumption. Further, the number of diodes and resistors in the triangular-to-sinusoidal converter affects the surface area of the converter. In addition, an integrator, which requires a device with large capacitance, also affects the surface area. Not surprisingly, then, the surface area is typically large in comparison to the surface area taken by other elements in a circuit.
More specifically, the conventional triangular-to-sinusoidal converter comprises several sub-stage elements. The first sub-stage element comprises an up-down counter with an input and output. A continuous triangular wave is fed into the up-down counter input and converted into a digital triangular wave which is made available on its output. A second sub-stage element is coupled to the output of the first sub-stage element. The second sub-stage element is a read only memory (“ROM”), also having an input and an output. The digital triangular waveform is taken from the output of the first sub-stage element and is fed into the input of the ROM. The digital triangular wave is converted into a digital sinusoidal waveform and made available on the output of the ROM. A third sub-stage element coupled to the output of the second sub-stage element is a digital-to-analog converter. The third sub-stage element accepts the digital sinusoidal waveform and converts it to a continuous analog sinusoidal waveform at the output. The fourth sub-stage element is a post analog filter with an input and an output. It accepts the continuous sinusoidal waveform on the input and outputs a smoother sinusoidal signal. As noted, the sinusoidal waveform generator disadvantageously requires a large surface area for the placement of its constituent components. The high power consumption of the triangular-to-sinusoidal waveform generator is attributable to the requirements of the up-down counter, read only memory, digital to analog converter and post analog filter.